1. Technical Field
The embodiments disclosed herein relate to a stereoscopic image display.
2. Discussion of the Related Art
A glasses type stereoscopic image display for displaying three-dimensional (3D) images is classified into a polarized glasses type stereoscopic image display and a shutter glasses type stereoscopic image display. The polarized glasses type stereoscopic image display requires a polarization separation device, such as a patterned retarder, to be attached to a display panel. The patterned retarder separates polarized light of a left eye image and a right eye image displayed on the display panel. A viewer wears polarized glasses when viewing a stereoscopic image on the polarized glasses type stereoscopic image display. Hence, the viewer sees polarized light of the left eye image through a left eye filter of the polarized glasses and polarized light of the right eye image through a right eye filter of the polarized glasses, resulting in the viewer experiencing a stereoscopic feeling.
The display panel of the existing polarized glasses type stereoscopic image display may use a liquid crystal display panel. A parallax is generated between a pixel array of the liquid crystal display panel and the patterned retarder due to a thickness of an upper glass substrate of the liquid crystal display panel and a thickness of an upper polarizing plate, and thus leads to a poor vertical viewing angle. When the viewer views a stereoscopic image displayed on the polarized glasses type stereoscopic image display at a vertical viewing angle higher or lower than the front of the liquid crystal display panel, the viewer may perceive 3D crosstalk, where the left eye image and the right eye image overlap each other, when viewing the stereoscopic image with a single eye (i.e., the left eye or the right eye).
To solve the problem of the 3D crosstalk at the vertical viewing angle in the polarized glasses type stereoscopic image display, Japanese Laid Open Patent Publication No. 2002-185983 proposed a method for forming black stripes on a patterned retarder (or 3D film) of a stereoscopic image display. In a method different from this method, the width of black matrices formed on a liquid crystal display panel can be increased. However, the formation of the black stripes on the patterned retarder may result in a reduction in luminance of two-dimensional (2D) and 3D images, and the black matrices may interact with the black stripes, thereby generating a Moiré pattern. Further, an increase in the width of the black matrices may reduce an aperture ratio, thereby reducing the luminance of the 2D and 3D images.
To solve the problem of the black stripes, a technology for dividing each of pixels of a display panel into two parts and controlling one of the two parts as a switchable black stripe was disclosed in U.S. Patent Application Publication No. US 2010/0265230 corresponding to U.S. patent application Ser. No. 12/536,031 filed on Aug. 5, 2009. The stereoscopic image display proposed by the present applicant divides each of the pixels into the two parts and writes 2D image data to each of the divided pixels in a 2D mode to thereby prevent a reduction in a luminance of a 2D image, and also widens a vertical viewing angle of a 3D image in a 3D mode. Hence, the stereoscopic image display proposed by the present applicant may improve the visibility of both the 2D and 3D images and may provide more excellent display quality than the existing stereoscopic image display. The switchable black stripe may include a thin film transistor (TFT) and a liquid crystal cell.
In the switchable black stripe technology, which has been already proposed by the present applicant, a voltage of the liquid crystal cell has to be discharged to a voltage of a black gray level in the 3D mode. To this end, a relatively high 3D control voltage of DC type may be applied to a gate electrode of the TFT of the switchable black stripe, so that an on-current may flow in the TFT of the switchable black stripe for a predetermined period of time. In this instance, the TFT of the switchable black stripe may undergo degradation of driving characteristics, including a shift of a threshold voltage, because of its gate bias stress.
The 3D control voltage of the switchable black stripe may be converted from the DC type to AC type in consideration of the problem. Hence, the gate bias stress of the TFT may be compensated. However, a gate voltage of the TFT may change because of the coupling between a line supplied with the 3D control voltage and a common electrode supplied with a common voltage. Hence, the common voltage may change, and luminance of the pixels may change. As a result, when the luminance of the pixels changes due to the changes in the 3D control voltage, a noise may appear in the display panel.